The slide-type extractors are conventionally used for conveying mineral materials in pieces or in granules from silos towards systems of treatment such as grinders, crushers, transporters or others in a continuous or a discontinuous manner.
In sand production lines, it is for example known to uniformly supply, with a slide-type extractor, the feed hoppers of the crushers or the grinders.
The slide-type extractors allow to adjust the flow rate accurately, have a simple structure and design making the maintenance easy and economical, a low useful power, and reduced overall dimension and investments.
If in the majority of cases, the slide-type extractors are used for granular mineral materials at ambient temperatures, it is known to use these extractors for granular mineral materials at high temperature. By “high temperature” we mean a temperature of several hundred degrees, or even greater than 1000° C.
FIG. 1 represents a device 2 for the extraction of granular mineral materials contained in a shaft furnace 4 and the transfer in a continuous furnace 6, known from the document FR2928643.
This device 2 includes a fixed upper part 8 and a mobile lower part 10 delimiting a duct 12 for the flow of granular mineral materials. This duct 12 is provided with an inlet mouth 14 connected to the shaft furnace 4 and an outlet mouth 16 connected to the continuous furnace 6. The inlet 14 and outlet 16 mouths are vertically and horizontally offset.
The mobile part 10 is movable in a direction 18 between an advanced position and a retracted position, to allow the flow of granular mineral material in the duct 12.
The device 2 includes a cylinder 20 forming reciprocating movement means of the mobile part 10 and rails 22 associated with rollers 24 mounted on the mobile part 10 forming means for guiding this mobile part 10.
A disadvantage of the device 2 is that the fixed 8 and the mobile 10 parts are likely to dilate under the effect of heat, and consequently to deform irreversibly. In these conditions, the relative movement of the mobile part 10 relative to the fixed part 8 may deteriorate over time. In addition, the abrasive nature of mineral materials quickly wears the fixed 8 and mobile 10 parts. Thus, the device 2 generates consequent maintenance costs for the operator.
Another disadvantage of the device 2 is that the hermeticity of the duct 12 is unsatisfactory. In these conditions, an ambient air flow enters this duct 12 and lowers the temperature of the granular mineral materials. The energy consumption of the continuous furnace 6 must then be increased in order to bring the granular mineral materials to a temperature in the order of 1250 to 1450° C., necessary to obtain a clinker. This energy overconsumption generates a cost for the operator and is detrimental to the environment.